Method of removing cavities from sheet metal



- Dec. 22, 1936. R, JOHNSTON 2,065,461

METHOD OF REMOVING GAVITIES FROM SHEET METAL Filed April 16, 1934 l wwww[wen/Z02: EOBEET F JOHNS TON,

@ am u WQXA/ Patented Dec. 22, 1936 PATENT OFFICE METHOD OF REMOVINGOAVITIES FROM SHEET METAL Robert F. Johnston, McKeesport, Pa., assignorto American Sheet and Tin Plate Company, a

corporation of New Application April 16,

1 Claim.

This invention relates to a method of removing pits or cavities fromsheet metal so as to provide at least one side surface of thesheet-which may be polished to a high degree, and while not limitedthereto the invention is particularly adapted for use in finishing alloysheets, such as stainless steel.

In the manufacture of sheet metal, and especially those sheets on whichit is necessary to provide at least one perfect side surface, such asfor use in the manufacture of automobile bodies, automobile radiatorshells and the like, great care and precaution must be exercised inorder not to dent or mar the surface, and even when the utmostprecaution is used some sheets will have there surfaces marred by dentsor pits which prohibit such surfaces from being polished to a highdegree.

Sheets having cavities in their surface are not prime sheets and todiscard these sheets or to sell them as seconds entails a considerableloss to the manufacturer, especially when such sheets are composed ofthe expensive stainless alloys.

The present invention provides a method of removing the dents or pitsfrom one side of the sheets so that substantially all sheets may beprovided with a highly polished surface and may be soldas prime sheets,thus reducing the manuiacturers loss to a minimum.

In the drawing illustrating one form of apparatus for carrying out themethod of my invention Figure 1 is a side elevation; and

Figure 2 is an enlarged fragmentary detail in section through thedent-removing head of the apparatus.

Referring more particularly to the drawing, the numeral 3 designates ahorizontally extending table for supporting the sheet metal from whichcavities are to be removed, which table is supported at its rear end ona wall W, or other suitable support, and at its forward end by anextension leg 2 and brackets 5. The extension leg 2 is locked in arecess in the forward end of the table 3 by a set-screw l. An anvil orpunch block I is mounted in the recess in the forward end of the table 3above the upper end of the leg 2, and is provided with a centrallyarranged adjustable punch 6. The upper end or operating point I of thepunch 6 is preferably composed of hardened tool steel or a diamond so asto resist wear, and readily operate upon alloy sheets.

The table 3 is provided with anti-friction casters or rollers I9 whichproject slightly above its surface and on which the sheet beingprocessed Jersey 1934, Serial No. 720,843

is adapted to ride. The punch point 1 is preferably slightly below theplane along the upper faces of the rollers I9, so that the sheet beingprocessed may be readily moved over the punch.

A bracket It! extends outwardly from the wall W spaced slightly aboveand parallel with the table 3, and terminates at its forward end in asleeve-like terminal 9. The bracket III has its forward end supported bya bracket 5 also extending outwardly from the wall. A circular dieplunger 8 is mounted for vertical movement within the sleeve portion 9of the bracket I0 and is normally urged upward by a coiled spring I4.The die 8 is provided with a central bore in which is mounted acentering pin II having a reduced point portion II which projectsthrough a reduced lower end 8 of the bore in the die 8. The pin II isnormally urged downwardly by a coiled spring I2, the tension of which isadjustable by a screw block I3. The lower face of the die 8 ispreferably made concave, as, at 8*, forming a depression into whichmetal may flow or move when the sheet is forced against the punch I.

The spring I4 which normally urges the die 8 upwardly is positionedbetween shoulders 9 formed in the sleeve 9 and adjustable screw units I5and washer I5 A semi-circular head I6 is mounted in the screw units I5and is adapted to be engaged by a cam I8 carried by a lever I1 andmounted in a bracket support 20. When the lever I1 is moved forwardly bythe operator the cam I8 is rotated so as to force the head I6 and itsconnected die 8 downwardly against the sheet being processed.

In carrying out the method of this invention the sheet S to be processedis supported on the table 3 and is moved between the die 8 and the anvilblock I and its punch point 1. The operator will shift the sheet beingprocessed over the'casters or rollers I9 so as to locate a cavity to beremoved under the pin point H In the drawing the cavity is indicated bythe letter P. In order to correctly locate the cavity directly over thepoint 1 of the punch 8, the operator will move the lever Il forwardly,thereby moving the die 8 and centering pin II downwardly until the pointII of the pin I I enters the cavity to be removed. With the pin .point II in this position the operator will continue to pull the lever I'Iforward so as to cause the cam I8 to force the die 8 downwardly intoengagement with the sheet S and further force the sheet downwardlyagainst the punch point 1, thereby punching the metal immediately belowthe cavity P upwardly into the die II, and the metal surrounding thecavity P will also be removed upwardly into the concave lower face ofthe die 8 so that the cavity is filled with metal from the opposite sideof the sheet and the metal I immediately surrounding the cavity isslightly raised above the normal plane at the upper side of the sheet.This operation is continued for each cavity or pit in the upper side ofthe sheet, and after all of the cavities or pits have been filled inthis manner the sheet will be removed from the apparatus of thisinvention and polished in any suitable polishing machine (not shown) soas to grind down the raised portions in the upper surface of the sheetformed by the operation of the punch 8 and the die 8, thereby providinga polished side of the sheet with a continuous smooth surface free fromany indentations or cavities.

One feature of this invention is that since the apparatus is manuallyoperated the pressure applied to the die may be regulated in accordancewith the depth of each cavity to be removed which greatly facilitatesthe operation of the apparatus in the carrying out of the method.

What I claim is:

The method of removing a cavity from the surface of a metallic sheetwhich consists in displacing the surface of the cavity beyond the planeof the surface of the sheet said displacement being insunlcient to placethe opposite surface of the sheet in the plane of the first namedsurface thereof, and removing all of the displaced metal which is beyondthe plane of the first named surface of the sheet.

ROBERT 1". JOHNSTON.

